Xcode User Defaults unrecognized selector error

Question

I'm getting started to use User Defaults on Cocoa and I'm getting an [NSConcreteData alphaComponent]: unrecognized selector sent to instance 0x100123660 error. Here is the source code :

AppDelegate.m file :

- (void)awakeFromNib{
NSColor *myColor = [NSColor greenColor];
[PreferencesController setDefaultColor:myColor];
NSColor *color = (NSColor *)[PreferencesController defaultColor];
NSLog(@"Default color : %@ - %@",(NSColor *)color, [NSColor greenColor]);
[tableView setBackgroundColor:color];
[colorWell setColor:color];
}

PreferencesController.m file :

+ (NSColor *)defaultColor{
NSColor * aColor;
NSData *theData=[[NSUserDefaults standardUserDefaults]      valueForKey:TableViewBackgroundColorKey];
if (theData != nil)
    aColor = (NSColor *)[NSUnarchiver unarchiveObjectWithData:theData];
return aColor;
}

+ (void)setDefaultColor:(NSColor *)color{
NSData *theData=[NSArchiver archivedDataWithRootObject:[NSArchiver archivedDataWithRootObject:color]];
[[NSUserDefaults standardUserDefaults] setObject:theData  forKey:TableViewBackgroundColorKey];
}

The return value of the NSLog is :

<040b7374 7265616d 74797065 6481e803 84014084 8484074e 53436f6c 6f720084 84084e53
4f626a65 63740085 84016301 84046666 66660001 000186> - NSCalibratedRGBColorSpace 0 1 0 1

So the value returned by + (NSColor *)defaultColor is not an NSColor, and certainly not [NSColor greeenColor].

I'm also getting the error -[NSConcreteData alphaComponent]: unrecognized selector sent to instance 0x100184050, which I think must be caused by not returning an NSColor for the method mentioned.

Please help me to debug.

Thanks.

Answer 1

You'll have to handle NSColor in a special way, when storing it in user defaults. NSColor is not an object that can be represented in an property list; see Storing NSColor in User Defaults for code examples.